Detector system for unidentified substances

ABSTRACT

Disclosed herein is a method of identifying a unidentified substance, comprising directing light from a light emitting source directly upon a stationary unidentified substance; collecting fluorescence from the unidentified substance in a detector; wherein the detector comprises a lock-in detection system; analyzing the fluorescence; and identifying the unidentified substance. Disclosed herein is a detection system comprising a light emitting source; a circuit board; wherein the trigger is operative to trigger a pulse of electrons from the circuit board to the light emitting source; a detector; and a central processing unit, wherein fluorescence generated from an unknown unidentified substance that is illuminated by light from the light emitting source is collected in the detector and analyzed in the central processing unit.

BACKGROUND

This disclosure relates to a detection system for unidentifiedsubstances. In particular, this disclosure relates to a detection systemfor use in detecting the presence of proteins in a chemical spill or ina suspicious-looking stain.

When an unidentified or suspicious substance is first noticed (as theresult of a spill), first responders (e.g., firefighters, police) areoften called to the site. The first responders generally perform primarytests to try to identify whether the substance is a protein byperforming a standard protein test. This test generally takes up to 5minutes but uses reagents in order to make an identification. Sincereagents are used to make the identification, the user has to have adegree of knowledge in the use of reagents. In addition, the user has tobe able to identify and distinguish between reaction products of thereagents with the substance.

If the use of the reagent results in a positive detection of proteins, aHAZMAT (hazardous materials) team is called in to perform additionalsecondary tests. These tests provide additional details about thesubstance but are expensive and time-consuming. A significant portion ofthe time, hazardous proteins are never finally detected, thus resultingin a waste of time and resources. It is therefore desirable to have aprotein detection system that can be easily transported to the site of aspill, is fast and accurate, and does not require the use of a speciallytrained individual to make an identification of the contents of thespill.

SUMMARY

Disclosed herein is a method of identifying a unidentified substance,comprising directing light from a light emitting source directly upon astationary unidentified substance; collecting fluorescence from theunidentified substance in a detector; wherein the detector comprises alock-in detection system; analyzing the fluorescence; and identifyingthe unidentified substance.

Disclosed herein is a detection system comprising a light emittingsource; a circuit board; wherein the trigger is operative to trigger apulse of electrons from the circuit board to the light emitting source;a detector; and a central processing unit, wherein fluorescencegenerated from an unknown unidentified substance that is illuminated bylight from the light emitting source is collected in the detector andanalyzed in the central processing unit.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1( a) is a side view of a hand-held detector constructed inaccordance with an embodiment of the invention;

FIG. 1( b) is a perspective view of the front of the hand-held detectorof FIG. 1( a);

FIG. 1( c) is a perspective view of the back of the hand-held detectorof FIG. 1( a);

FIG. 2 is a side view of a hand-held detector constructed in accordancewith an embodiment of the invention;

FIG. 3 illustrates one manner of functioning of the hand-held detectorof FIG. 1( a) and FIG. 2;

FIG. 4 illustrates another manner of functioning of the hand-helddetector of FIG. 1( a) and FIG. 2;

FIG. 5 illustrates a flow diagram exemplifying a process for using aplurality of LEDs and a plurality of optical filter/photodetector pairsto detect an unidentified substance in accordance with an embodiment ofthe invention; and

FIG. 6 illustrates a flow diagram exemplifying a process for using aplurality of LEDs and a plurality of optical filter/photodetector pairsto detect an unidentified substance in accordance with an embodiment ofthe invention.

DETAILED DESCRIPTION

The use of the terms “a” and “an” and “the” and similar references inthe context of describing the invention (especially in the context ofthe following claims) are to be construed to cover both the singular andthe plural, unless otherwise indicated herein or clearly contradicted bycontext. The modifier “about” used in connection with a quantity isinclusive of the stated value and has the meaning dictated by thecontext (e.g., it includes the degree of error associated withmeasurement of the particular quantity). All ranges disclosed herein areinclusive of the endpoints, and the endpoints are independentlycombinable with each other. The term “operative communication” betweentwo units indicates that the two units communicate with one another. Theoperative communication can be of any kind such as for example,electrical communication, mechanical communication, thermalcommunication (e.g., convection), acoustic communication (e.g.,ultrasound, or the like), electromagnetic communication (e.g.,ultraviolet radiation, optical radiation, or the like), or the like, ora combination comprising at least one of the foregoing forms ofcommunication. Electrical communication comprises the flow of electronsbetween two units, while mechanical communication involves the transferof forces between two units via physical contact (e.g., via friction,adhesion, or the like) between the two units.

Disclosed herein is a detection system for the detection of unidentifiedsubstances. The detection system is hand-held and can be easilytransported to the site of a spill, is fast and accurate and does notrequire the use of a specially trained individual to make anidentification of the contents of the spill. The unidentified substancescan be in powder or liquid form. In one embodiment, the detection systemcomprises a plurality of light emitting sources for generating lightthat is focused on the unidentified substances via a reflector. Thereflector also acts as a light redirecting system for redirecting thelight reflected by or generated from the unidentified substances. Thedetection system then analyzes the light reflected by or generated fromthe unidentified substances and provides the user with a spectralidentification as well as the chemical identity of the unidentifiedsubstances. In one exemplary embodiment, the plurality of light emittingsources are LED's (light emitting diodes) that emit light in theultraviolet, visible and infrared regions of the electromagneticspectrum. In another exemplary embodiment, the detection system is a“point and click detection system” that can be provide an identificationof the unidentified substances at distances of up to 1 meter from thelocation of the unidentified substances.

As used herein, the term “unidentified substance” refers to anyindividual mass or collection of masses that can interact with energy,such as electromagnetic radiation, to produce signatures that can becollected and analyzed. The particles may be of varying scale. Forexample, the unidentified substance may be of an atomic scale or amolecular scale. At a larger scale, the unidentified substance may be aproteinaceous substance and may be a combination of molecules forming aspore, a virus, or a cell. For example, the unidentified substance mayinclude a biological fluorophore. The unidentified substance can beconsidered to include organic as well as inorganic matter. Theunidentified substance is generally stationary and does not exist in theform of a stream of particles that are mobile.

The categories of biological fluorophores include the aromatic aminoacids, proteins, tryptophan, tyrosine, phenylalanine, nicotinamideadenine dinucleotide compounds, flavins, chlorophylls, or the like, or acombination comprising at least one of the foregoing biologicalfluorophores. In an exemplary embodiment, the biological fluorophoresmay include proteins. For example, the biological fluorophores mayinclude tryptophan, riboflavin, bovine serum albumin, a nicotinamideadenine dinucleotide compound, or a combination comprising at least oneof the foregoing biological fluorophores. Biological particlescontaining these fluorophores comprise biological spores, vegetativebacteria, proteins, DNA, viruses, toxins, and fragments of theseparticles.

In one embodiment, the disclosure relates to a method for theenhancement of the discrimination of unidentified substances bymodulating one or more environmental parameters. In another embodiment,the fluorescence and/or phosphorescence signatures of the particles maybe compared with the reference signatures. In an exemplary embodiment, avariation in the detectable response of the unidentified substances maybe compared with a reference calibration curve to identify theunidentified substances. In certain embodiments, nicotinamide adeninedinucleotide hydrogen (NADH), indicative of biological activity orviability, may be coupled with information about fluorescence propertiesof other biological particles to detect the other unidentifiedsubstances.

With reference now to the FIGS. 1( a), 1(b) and 1(c), a detection system100 comprises a single reflector 102 disposed in a case 104. Thereflector 102 is disposed at the first end of the case 104. The secondend of the case is opposed to the first end of the case and comprises anoutput device 118 upon which chemical identifications can be displayed.Disposed at the center of the reflector 102 is a circuit board 106 uponwhich are disposed a light emitting source 202 and a photodiode 204. Thecircuit board 106 is in operative communication with an electronicsource 110 that supplies pulsed electrical charges that induce radiationin the light emitting source 202. The pulsing electronics 110 are inelectrical communication with a source of power 108 and with a centralprocessing unit (CPU) 114.

In one embodiment, the case 104 is a carrying case that comprises afirst end and a second end that are opposingly disposed to one another.The case 104 can be manufactured from an organic polymer, a ceramic, ora metal. The case 104 can comprise a single piece or can comprise aplurality of pieces that are in mechanical communication with oneanother. As can be seen from the FIGS. 1( a), 1(b) and 1(c), the case104 comprises a conduit that houses the reflector 102, the circuit board106, the power source 108, and the pulsing electronics 110. Thedetection system 100 also includes a trigger 112. In an exemplaryembodiment, the case 104 is provided with a handle 120 for transportingthe detection system 100. As can be seen from the FIG. 1( a), the handle120 is provided with a slot in which is disposed the trigger 112. Thetrigger 112 is used to activate the detection system 100. An alternateembodiment of a detection system is depicted in the FIG. 2. Thedetection system 100 includes a trigger comprising two buttons 113 foractivating the detector and an alternative design for the handle 120.

The case 104 can have any cross-sectional shape that permits the user toconveniently transport it. The cross-sectional shape can be circular,square, rectangular, triangular, polygonal, or the like. An exemplarycross-sectional shape for the case 104 is a circular shape, whichresults in the case 104 being cylindrical in geometry.

The detection system 100 can have any desired dimensions. In anexemplary embodiment, it is desirable for the detector to be a hand-helddetector. The detector can have a width (or diameter) of about 2 toabout 12 inches, while the length can be about 3 to about 20 inches. Ascan be seen in the FIG. 1( a), an exemplary detector can be a hand-helddetector, having a width (or diameter) of about 3 inches and a length ofabout 4 inches. Similarly, another exemplary hand-held detector may havea width of about 5 inches and a length of about 6 inches.

With reference now to the FIG. 3, the reflector 102 comprises a highlypolished inner reflective surface 103 that reflects light generated bythe light emitting source 202 towards the unidentified substance. Thereflector 102 can be parabolic, spherical, or elliptical in shape. Anexemplary reflector 102 is elliptical in shape. The reflective surface103 also reflects light reflected from the unidentified substancetowards the detector 204. The reflective surface 103 also reflects lighttoward the detector 204 that is generated by the unidentified substancevia a fluorescence process. The reflector 102 comprises a hole 116 atits center in which the circuit board 106 is disposed.

In one embodiment, the detector can comprise a single reflector. Inanother embodiment, the detector can comprise a plurality of reflectors.In yet another embodiment, the detector can comprise 2, 3, 4, 5, or morereflectors.

The reflector 102 generally has a focal point that permitsidentification of desired substances from a distance of about 1millimeter up to about 1 meter, specifically about 5 millimeters toabout 0.75 meter, more specifically about 1 centimeter to about 0.25meter, and even more specifically about 10 centimeters to about 15centimeters.

The circuit board 106 supports the light emitting source 202 and thedetector 204. In other words, the light emitting source 202 and thedetector 204 are disposed upon and are in intimate contact with thecircuit board 106. The circuit board 106 transmits electricity generatedin the pulsing electronics 110 to the light emitting source 202 and alsotransmits electricity generated in the detector 204 to the CPU 114 (FIG.1( a)) for analysis. In an exemplary embodiment as depicted in the FIG.3, the circuit board 106 can have disposed upon it a plurality of lightemitting sources 202, 206, 210, or the like, or a plurality ofphotodetectors 204, 208, 212, or the like. In one embodiment, the lightemitting sources 202, 206, 210, or the like, as well as the plurality ofphotodetectors 204, 208, 212, or the like, can be arranged on theprinted circuit board 106 in a variety of different geometricarrangements. For example, in one embodiment, the light emitting sources202, 206, 210, or the like, and the plurality of photodetectors 204,208, 212, or the like, can be arranged linearly as shown in the FIG. 1(a). In another embodiment, the light emitting sources and/or theplurality of photodetectors can be arranged in a circular, random,periodic or aperiodic fashion as may be desired.

The circuit board 106 upon which the light emitting sources are disposedcan be circuit board commercially available from the Bergquist Companywith flip-chipped LEDs.

As can be seen in FIGS. 1-3, the circuit board 106 is disposed at thegeometric center of the reflector 102 and passes through the hole at thegeometric center of the reflector 102. In one embodiment, the circuitboard 106 passes through the focal point of the reflector 102.

FIG. 4 depicts another exemplary embodiment of the detection system 300that does not employ a reflector. In this arrangement, a first circuitboard 302 provides an electrical pulse (generated by pulsingelectronics) to the light emitting source 202 to produce a first pulseof light. The light generated by the fluorescing of the unidentifiedsubstance is collected by the detector 204 and the electrical currentgenerated in the detector 204 is transmitted to the CPU for analysis bya second circuit board 304. Each light emitting source 202 and eachdetector 204 has disposed upon it a lens 306 for collimating theexcitation and for collecting the florescence. In this design, theelimination of the mirror renders the system more compact than thesystems displayed in FIGS. 1 and 2. In audition, the light emittingsources 202 can be arranged to be circular. A circular pattern wouldprovide an efficient spacing of the light emitting sources and thephotodetectors.

It should be appreciated that any suitable light emitting source 202 maybe utilized. It is desirable that the light emitting source 202 becapable of emitting a sufficiently high intensity light of the desiredwavelength. By “sufficiently high intensity light” is meant a light ofsufficient intensity to induce an effective optical signal, such asparticle fluorescence. The term “wavelength” should be understood toencompass a range of wavelengths and to refer to a spectral range ofelectromagnetic energy. In an exemplary embodiment, the light emittingsource 202 can include multi-wavelength ultraviolet (UV), visible and/orinfrared (IR) electromagnetic radiation emitters. Infrared radiationemitters may be used for heating unidentified substances in order toactivate fluorescence at different wavelengths from the samples.Furthermore, the light emitting source 202 may be pulsed to achieve thedesired intensity of light without sacrificing reliability or lifetime.Another advantage of a very fast pulsed source, such as a light emittingdiode (LED), would be to synchronize the detector to the source for thepurpose of improving the signal to noise ratio. A heat sink may beattached to the light-emitting source 202 to enhance heat dissipation.

Examples of suitable light emitting sources 202 are light emittingdiodes, including surface-emitting light emitting diodes, ultravioletlight emitting diodes, edge-emitting light emitting diodes, resonantcavity light emitting diodes, broad band light emitting diodes,flip-chipped light emitting diodes, gas-discharge lamps, mercury lamps,filament lamps, black-body radiators, chemo-luminescent media, organiclight emitting diodes, phosphor upconverted sources, plasma sources,solar radiation, sparking devices, vertical light emitting diodes,wavelength-specific light emitting diodes, lasers, laser diodes, or thelike, or a combination comprising at least one of the foregoing lightemitting sources. Exemplary light emitting sources are UV-visible lightemitting sources 202.

Examples of suitable LEDs that are used for the emission of light arealuminum gallium arsenide (AlGaAs)—red and infrared color; aluminumgallium phosphide (AlGaP)—green color; aluminum gallium indium phosphide(AlGaInP)—high-brightness orange-red, orange, yellow, and green colors;gallium arsenide phosphide (GaAsP)—red, orange-red, orange, and yellowcolors; gallium phosphide (GaP)—red, yellow and green colors; galliumnitride (GaN)—green, pure green (or emerald green) colors, and blue alsowhite (if it has an AlGaN or InAlGaN quantum well); indium galliumnitride (InGaN)—near ultraviolet, bluish-green and blue colors; siliconcarbide (SiC) as substrate—blue color; silicon (Si) as substrate bluecolor; sapphire (Al₂O₃) as substrate—blue color; zinc selenide(ZnSe)—blue color; diamond (C)—ultraviolet color; aluminum nitride(AlN); aluminum gallium nitride (AlGaN)—near to far ultraviolet, or acombination comprising at least one of the foregoing LEDs. In oneembodiment, packaged LEDs comprising their own optics, such as, forexample, ball shaped lenses, may be used.

The light emitting source 202 generally emits radiation having awavelength that promotes fluorescence in the unidentified substances.The light emitting source 202 may emit radiation having a wavelength ofabout 100 nanometers (nm) to about 1,000 nm. An exemplary wavelength forthe light emitting source 202 is about 200 to about 450 nm.

The light emitting source 202 generally can be activated to emitelectromagnetic radiation upon the application of a voltage of about 1to about 20 volts. An exemplary voltage is about 4 to about 9 volts.

An optional optically transparent window 122 (FIG. 1( a)) may be locatedat the end of the case 104 opposing the end including the output device118. The optically transparent window 122 encloses the circuit board 106and may include an optical filter for lessening the amount of parasiticlight that is in the range of the detection spectrum from impinging uponthe reflector 102 and producing parasitic signals in the form ofscattered light.

The detector 204 can be a photodetector that can capture a single photonor a collection of single photons. Examples of suitable photodetectorsare photoconductors, photodiodes, photomultiplier tubes, an avalanchephotodiodes, any photodetector capable of detecting single photons orcollections of single photons, or a combination comprising at least oneof the foregoing photodetectors. The detector 204 may also comprisecharge coupled device (CCD) imagers, spectral imagers, or a combinationcomprising at least one of the foregoing detectors. An exemplaryphotodetector is a filtered photodiode commercially available fromHamamatsu. As noted above, both the light emitting source 202 and thedetector 204 can optionally have disposed upon them a lens thatcollimates the excitation from the light emitting source as well as forcollecting the florescence from the unidentified substances.

The pulsing electronics 110 supply a voltage to the light emittingsource 202 via the circuit board 106. The application of the appropriatevoltage to the light emitting source 202 promotes the light emittingsource to emit light in the UV, visible and infrared regions of theelectromagnetic spectrum. The pulsing electronics 110 are generallyactivated upon the depression of the trigger 112. Upon depressing thetrigger 112, a power source 108 supplies power to the pulsingelectronics 110. The power source 108 is generally a commerciallyavailable battery that is capable of supplying a voltage of about 12volts. The pulsing electronics 110 supplies power to the light emittingsources 102 to emit light as detailed above.

In an exemplary embodiment, the pulsing electronics 110 generally supplythe requisite voltage that activates the light emitting sources. Thesevoltages are indicated above. The pulsing electronics 110 supply theaforementioned voltages to the light emitting sources at currents ofabout 1 to about 400 milliamperes (mA). An exemplary amount of currentused to activate the light emitting sources is about 20 to about 100 mA.The pulsing electronics 110 pulse the light emitting sources at afrequency of about 10 to about 10,000,000 hertz (Hz). In an exemplaryembodiment, the pulsing electronics 110 pulse the light emitting sourcesat a frequency of about 10,000 to about 100,000 Hz. The pulsingelectronics 110 can be commercially purchased from Supertex. The pulsingof the light emitted from the light emitting source 202 facilitates areduction in the background noise thereby improving signal resolutionand consequently sample identification.

The CPU 114 generally functions to process electrical signals generatedin the detector 204 and converts these signals into a spectrum thatindicates the identity of the unidentified substance. The CPU 114generally comprises an analysis system (not shown) that receives signalsfrom the detector 204 and conveys the signals to the output device 118.The analysis system may be a univariate analysis system, or amultivariate analysis system.

Where the optical spectrum comprises several wavelengths or an entirespectrum over a certain range, the optical characteristics of theunidentified substance may be determined using multivariate calibrationalgorithms such as Partial Least Squares Regression (PLS), PrincipalComponents Regression (PCR), and the like.

Given a large enough span of calibration samples, multivariatecalibration models are generally more robust than univariate models dueto enhanced outlier detection capabilities and increased tolerancetoward slight shifting in peak position or band shape. In addition,multivariate calibration models allow for measurement of more than onevariable or component of interest from the unidentified substance. PLSmodels correlate the sources of variation in the spectral data withsources of variation in the sample. Preferably, the PLS model isvalidated by statistical techniques.

Examples of statistical techniques are leave one out cross-validation,Venetian blinds, random subsets, or a combination comprising at leastone of the foregoing statistical techniques. All or part of the steps inthe analysis of response of optical signals from the particle stream maybe coded or otherwise written in computer software, in a variety ofcomputer languages including, but not limited to, C, C++, Pascal,Fortran, Visual Basic®, Microsoft Excel, MATLAB®, Mathematica®, Java, orthe like. Results may be illustrated using known pattern recognitiontools.

The output device 11 may include a display (e.g., a screen) or printer,to output the signatures generated during the identification of theunidentified substances. In an exemplary embodiment, the second end ofthe case 104 may comprise a cover 117 that further comprises an outputdevice 118. An exemplary output device is a screen that can be used toproduce a spectrum of the fluorescence generated by the unidentifiedsubstance. The screen can also identify the unidentified substance byname or Chemical Abstract number.

As noted above, the detection system comprises a point and clickdetection system. In an exemplary embodiment, in one manner ofproceeding, the hand-held detection system 100 is pointed at asuspicious substance on a surface such as the floor. Upon activating thetrigger 112, a pulse of electricity is generated in the pulsingelectronics 110. The pulse of electricity travels to the circuit boardactivates the light emitting source 202 which emits light of aparticular desired frequency. The light is reflected by the reflector102 and impinges upon the suspicious substance. Fluorescence from thesuspicious substance is collected by the detector 204 and transmitted.

In one exemplary embodiment, the light emitting source 202 and thedetector 204 may be tuned to the absorption and emission profiles ofvarious particles. For example, a first light emitting source 202, mayemit light at a first wavelength at which a predetermined particlefluoresces while a second light emitting source 206 may emit light at asecond wavelength at which a second predetermined particle fluoresces.It should be appreciated that certain particles fluoresce at more thanone wavelength, and thus the first and second predetermined particlesindeed may be the same particles. Alternatively, each of the lightemitting sources 202, 206, 210 may emit light at a wavelength at whichseveral types of particles fluoresce and each of the detectors 204, 208,212 are tuned to detect the fluorescent light at wavelengths differingfrom the other of the detectors 204, 208, 212.

When several excitation wavelengths are employed and correspondingemission spectra are collected, this collection of spectra constitutesan excitation-emission map. Suitable methods for determination offluorescence-excitation maps are provided in for example, U.S. Pat. Nos.6,166,804 (Potyrailo et al.) and 6,541,264 (Potyrailo et al.).Fluorescence excitation-mission maps are useful because they provide amore comprehensive spectral signature for a single species and provide amore detailed capability to reveal if more than one fluorescent speciesare present in a measured sample.

For example, a 280 nm ultraviolet (UV) source and a 365 nm UV source canbe turned on alternatively such that a unidentified substance is hitwith one UV wavelength at a time. Bacteria will fluoresce primarily inthe 340 nm range, due to protein fluorescence, upon exposure to 280 nmUV radiation. Bacteria will also fluoresce primarily in the 430 to 550nm range upon excitation with 365 nm UV light, due to NADH and flavinfluorescence. In contrast, many common fluorescent interferents, such asdiesel soot and many vegetable oil aerosols, show significantfluorescence at only one of these excitation wavelengths. Thus, with onephoto detector optically filtered at 340 nm and another photo detectoroptically filtered at 430-550 nm, a sufficient algorithm can bedeveloped for discriminating airborne bacteria from common interferents.Table 1 provides a summary of fluorescence ranges for bio-agents andcommon interferents exposed to light at various wavelengths.

TABLE 1 Agent λ_(excit) = 280 nm λ_(excit) = 340/365 nm λ_(excit) = 405nm Vegetative Tryptophan (320-360 nm); NADH + Flavins Flavins (500-600nm) Bacteria Flavins (430-600 nm) (500-600 nm) Spores Tryptophan &Possible NADH, Flavins (500-600 nm) Flavins but dim Viruses Tryptophan &Non-detectable Non-detectable Flavins Toxins Tryptophan Non-detectableNon-detectable Vegetable Oil Non-detectable 400-550 nm 450-500 nm DieselSoot Dim 380-500 nm Dim 380-500 nm 410-650 nm Fluospheres Dim 280 nm400-500 nm Non-detectable Road Dust Non-detectable Non-detectableNon-detectable

In another embodiment, depicted in the schematic flow chart in the FIG.5, a plurality of LEDs and a plurality of optical filter/photodetectorpairs may be used to detect an unidentified substance. In the FIG. 5, inthe steps 402, 404, 406, 408, 410, 422 and 424, a first light emittingsource 202 (e.g., a LED) is pulsed and a first detector 204 and/or asecond photodetector 208 (e.g., a photodiode) is arranged to detect thelight arriving at this first detector over the period of operation ofthe first light emitting source 202 in addition to a small delay (e.g.,in nanoseconds) associated with a fluorescence process from the sample.

Often, there are situations when measurements of analytical signal fromthe powder sample are performed in presence of unwanted opticalinterference. A non-limiting example of unwanted optical interference isambient light. Several methods that are applicable to the rejection ofunwanted optical radiation from interfering with measurements of ananalytical signal include lock-in detection, temporal gating,polarization gating, phase resolved optical detection, Fourier transformfiltering, or the like, or a combination comprising at least one of theforegoing.

In one embodiment, the detector is gated to detect light associated witha fluorescence process from the sample. In another embodiment, thedetector is a photodetector with an optical filter that selectivelypermits the detection of light having a specific wavelength.

In yet another embodiment, the arrival of light (associated with afluorescence process from the sample) is detected by the use of alock-in detection technique. Lock-in detection is a technique to recovera signal even in the presence of broad band noise whose magnitude isseveral times greater than the signal itself. When lock-in detection isused, the photodetector is locked into frequency of the light source,not just gated, this allows a virtually blind response to the ambientlight and a very high signal to noise ratio. In lock-in detection, alight from the light emitting source is pulsed and a photodetector islocked to a frequency of the pulse and operates to detect light with aselected time gate width. In another embodiment, a light from the lightemitting source is pulsed and a signal to the photodetector is amplifiedwith a lock-in amplifier at the frequency at which the light from thelight emitting source is pulsed.

As a result, all sources can be pulsed simultaneously at differentfrequencies. This approach provides a lock-in detection of lightdetected with the photodetector only after pulsing of an LED andsignificantly reduces or eliminates effects of ambient light on thedevice performance. The effects of ambient light that provide elevatedbackground signals are therefore minimized. Without gating of thephotodetector after LED pulsing, these background signals are too highto detect weak fluorescence signals from a sample.

A second light emitting source 206 is then pulsed and a second detector208 is gated (in steps 412, 414, 416, 418, 420, 422 and 424) to detectthe light arriving at the second detector 208 over the time of operationof the second light emitting source 206 plus a small delay (innanoseconds) associated with a fluorescence process from the sample. Inthis embodiment, the first light emitting source 202 and the secondlight emitting source 206 are emitting at different wavelengths and thefirst detector 204 and the second detector 208 are detecting light atdifferent emission wavelength regions.

In yet another exemplary embodiment not depicted in the FIG. 5, thefirst light emitting source 202 and the second light emitting source 206are emitting at different wavelengths and only one detector 204 is usedthat detects light in a broad wavelength region, of about 200 to about1000 nm, more specifically about 220 nm to about 900 nm, and even morespecifically about 230 nm to about 850 nm.

In yet another embodiment depicted in steps 500-504 in the schematicflow diagram of FIG. 6, in addition to using the first light emittingsource 202 and the detector 204 for fluorescence detection, a secondlight emitting source 204 (step 506) (denoted as “heater” in FIG. 6) isused to heat the unidentified sample. This second light emitting source204 can be an infrared LED source, or a infrared laser diode. Thissecond light emitting source 204 serves as a heater, to heat theunidentified sample locally. Heating the sample can give rise tofluorescence at different wavelengths, which can be used to improvedetection capabilities (steps 508-514).

In summary, the detection system 100 can be used in a variety of ways toidentify unknown unidentified substances. In one embodiment, a pluralityof light emitting sources can be used in conjunction with a singledetector. In another embodiment, a single light emitting source can beused in conjunction with a plurality of detectors. In yet anotherembodiment, a plurality of light emitting sources can be used inconjunction with a plurality of detectors. In yet another embodiment aplurality of light emitting sources can be pulsed sequentially orsimultaneously while a single detector or a plurality of detectors canbe gated to detect the fluorescence generated by the unidentifiedsubstances. The gating of the detectors can be programmed to occursimultaneously or sequentially.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A method of identifying a unidentified substance, comprising:directing light from a light emitting source directly upon a stationaryunidentified substance; collecting fluorescence from the unidentifiedsubstance in a detector; wherein the detector comprises a lock-indetection system, wherein the light emitting source heats theunidentified substance prior to collecting the fluorescence; analyzingthe fluorescence; and identifying the unidentified substance.
 2. Themethod of claim 1, wherein the light emitting source is a light emittingdiode.
 3. The method of claim 2, wherein the light emitting diode is asurface-emitting light emitting diode, broad band light emitting diodes,ultraviolet light emitting diode, edge-emitting light emitting diode,resonant cavity light emitting diode, flip-chipped light emitting diode,organic light emitting diode, vertical light emitting diode,wavelength-specific light emitting diode, laser light emitting diode, ora combination comprising at least one of the foregoing light emittingdiodes.
 4. The method of claim 1, wherein the unidentified substance isnot in the form of a stream of particles.
 5. The method of claim 1,wherein the light from the light emitting source has a wavelength ofabout 200 to about 450 nanometers.
 6. The method of claim 1, wherein thelight is emitted from a plurality of light emitting sources and whereinthe light emitting sources emit light simultaneously or sequentially. 7.The method of claim 1, wherein the fluorescence is collected by aplurality of detectors either simultaneously or sequentially.
 8. Themethod of claim 1, wherein the light is emitted from a plurality oflight emitting sources and wherein the light emitting sources emit lightsimultaneously or sequentially and wherein the fluorescence is collectedby a single detector.
 9. The method of claim 1, wherein the light isemitted from a single light emitting source and wherein the fluorescenceis collected by a plurality of detectors either simultaneously orsequentially.
 10. The method of claim 1, wherein the light is emittedfrom a plurality of light emitting sources and wherein the lightemitting sources emit light simultaneously or sequentially and whereinthe fluorescence is collected by a plurality of detectors eithersimultaneously or sequentially.
 11. The method of claim 1, wherein thedetector is a photodetector.
 12. The method of claim 1, wherein thedetector is a photoconductor, a photodiode, a photomultiplier tube, anavalanche photodiode, or a combination comprising at least one of theforegoing photodetectors.
 13. The method of claim 1, further comprisingtransmitting an electrical signal to the light emitting source prior tothe focusing of the light.
 14. The method of claim 1, further comprisingpulsing the light from the light emitting source.
 15. The method ofclaim 1, further comprising gating the detector to receive thefluorescence in pulsed form.
 16. The method of claim 1, wherein thelight from the light emitting source further impinges on a reflector.17. The method of claim 16, wherein the light impinges on a reflectorprior to being focused on the unidentified substance.
 18. The method ofclaim 1, wherein the fluorescence from the unidentified substancefurther impinges on a reflector.
 19. The method of claim 18, wherein thefluorescence from the unidentified substance impinges on a reflectorprior to being focused on the detector.
 20. The method of claim 19,further comprising transmitting an electrical signal from the detectorto a central processing unit.
 21. The method of claim 1, wherein heatingis performed to heat an unidentified substance to a temperature above anambient temperature of the sample.
 22. The method of claim 21, whereinheating is performed to heat an unidentified substance to a temperatureof at least 50°C. above a temperature of the sample.
 23. A method ofidentifying a unidentified substance, comprising: directing light from alight emitting source directly upon a stationary unidentified substance,wherein the light is emitted from a plurality of light emitting sourcesand wherein the light emitting sources emit light simultaneously orsequentially; collecting fluorescence from the unidentified substance ina detector; wherein the detector comprises a lock-in detection system;analyzing the fluorescence; and identifying the unidentified substance.24. A method of identifying a unidentified substance, comprising:directing light from a light emitting source directly upon a stationaryunidentified substance; collecting fluorescence from the unidentifiedsubstance in a detector; wherein the detector comprises a lock-indetection system, wherein the fluorescence is collected by a pluralityof detectors either simultaneously or sequentially; analyzing thefluorescence; and identifying the unidentified substance.
 25. A methodof identifying a unidentified substance, comprising: directing lightfrom a light emitting source directly upon a stationary unidentifiedsubstance; collecting fluorescence from the unidentified substance in adetector; wherein the detector comprises a lock-in detection system,wherein the light is emitted from a plurality of light emitting sourcesand wherein the light emitting sources emit light simultaneously orsequentially and wherein the fluorescence is collected by a singledetector; analyzing the fluorescence; and identifying the unidentifiedsubstance.
 26. A method of identifying a unidentified substance,comprising: directing light from a light emitting source directly upon astationary unidentified substance; collecting fluorescence from theunidentified substance in a detector; wherein the detector comprises alock-in detection system, wherein the light is emitted from a singlelight emitting source and wherein the fluorescence is collected by aplurality of detectors either simultaneously or sequentially; analyzingthe fluorescence; and identifying the unidentified substance.